Spr 838

We compared the effect of preconditioning with riociguat on the hemodynamic parameters of the donor heart before explantation as described earlier^{14 (link)}. A 2 F microtip pressure microcatheter (SPR-838, Millar Instruments, Houston, TX, USA) was used to carry out invasive hemodynamic measurements^{39 (link),40 (link)}. Sampling rate for these measurements was set to 1000 samples/s using a pressure-volume (P-V) conductance system (MPVS-Ultra, Millar Instruments) and the PowerLab 16/30 data acquisition system (AD Instruments, Colorado Springs, CO, USA). Animals were anesthetized with 1–2% isoflurane, and were placed on heating pads to maintain core temperature at 37 °C. The left external jugular vein was cannulated with a polyethylene catheter for fluid administration. At initiation of the measurements, mean arterial blood pressure (MAP) and heart rate (HR) were recorded, which was followed by advancement of the catheter into the left ventricle (LV) under pressure control. We used only the pressure signal of the microcatheter to calculate the maximal slope of systolic pressure increment (dP/dt_max) and diastolic pressure decrement (dP/dt_min) with a special P-V analysis program (PVAN, Millar Instruments).

For determination of effective arterial elastance (Ea), rats were anesthetized in an induction chamber with 2-3% isoflurane, and anesthesia was maintained so that toe-pinch, tail-pinch and palpebral reflexes were absent (2-3% isoflurane delivered by 100% O₂ mask inhalation). Rats were placed on a controlled heating pad to maintain a body temperature of 37°C, and a 2.0 F microtip pressure-volume catheter (SPR-838; Millar Instruments; Houston, TX) was introduced via the right carotid artery into the left ventricle (LV) as previously described [27 (link)]. After a 20 minute stabilization period, LV pressure-volume loops were recorded using the MPVS 400 pressure-volume conductance system (Millar Instruments) at a sampling rate of 1000/sec for 30 sec. 15–20 pressure-volume loops were subsequently selected and analysed using a cardiac pressure-volume analysis program (PVAN 3.5; Millar Instruments) as previously described [27 (link)]. Ea was calculated as the ratio of end systolic pressure to stroke volume and normalized to body weight resulting in the arterial elasticity index (EaI) [10 (link)].

Animals were anesthetized with 3–4% isoflurane and placed on controlled heating pads. RV systolic pressure (RVSP) was measured by advancing a curved-tip pressure transducer catheter, 2F (SPR-513, Millar Instruments) for rats and 1F (SPR-1000, Millar Instruments) for mice, into the RV via the right jugular vein under 1–2% isofluorane anesthesia. In rats, cardiac output was assessed by advancing a 2F microtipped PV catheter (SPR 838, Millar Instruments) into the left ventricle through the right carotid artery under 1.5–2% isofluorane anesthesia. Cardiac index (CI) was calculated by dividing cardiac output by body weight. Total pulmonary vascular resistance index (TPRI) was estimated by dividing RVSP by CI^{35 (link)}. Heart and lungs were collected en bloc and lungs were perfused with physiological saline via the RV outflow tract to flush the blood cells from the pulmonary circulation. RV hypertrophy was determined by calculating the weight ratio of the RV free wall to the combined left ventricle and septum (Fulton index). Values shown for hemodynamic parameters and Fulton index from rats treated with sildenafil monotherapy are historical data from our laboratory.

One hour after transplantation a 3F latex balloon catheter (Edwards Lifesciences Corporation, Irvine, CA, USA) was introduced into the left ventricle via the apex to determine maximal left ventricular (LV) systolic pressure (LVSP), maximal slope of the systolic pressure increment (dP/dt_max) and diastolic pressure decrement (dP/dt_min) and heart rate (HR) by a Millar micromanometer (SPR-838, Millar Instruments) at different LV volumes (20–160 µl). From these data LV pressure-volume relationships were constructed. Coronary blood flow (CBF) of the graft was measured by an ultrasonic flow meter (Transonic Systems Inc., Ithaca,USA) mounted on the donor ascending aorta.

Under anesthesia by ketamin (80 mg/kg, i.p.) and xilazin (15 mg/kg, i.p.), a pressure–volume catheter (SPR-838, Millar Instruments, Houston, TX, USA) connected to a pressure transducer (MLT884, ADInstruments, Inc., Colorado Springs, CO, USA) was introduced through the jugular vein in the rats. The RV systolic pressure (RVSP) was recorded on a computer for analysis using Lab Chart software (Version 7.0, ADInstruments, Inc.). At the end of the experiment, animals were euthanized, and heart and lungs were removed.

Briefly, the right carotid artery was isolated and catheterized with a 2Fr pressure–volume (PV) conductance catheter (SPR-838, Millar Instruments, TX, USA) and advanced retrograde into the LV. The left jugular vein was also cannulated for fluid replacement and hypertonic saline bolus infusion. Subsequently, the abdomen was opened and loose ligatures placed around the inferior vena cava (IVC) and portal vein to facilitate pre-load reduction [27 (link)].